Help!! Multiple Misfires!

[TantricLT4]

My 96 LT4 is throwing codes! I had the opti-spark and water pump replaced at my local GM dealership - they checked the plugs, and plug wires while they were there. I've had it to them twice already and have paid an enormous bill. Everytime I leave the dealership it shows that I'm not throwing any codes. The next day my Check Engine light comes on. I took it back to them and they are wanting to keep it for a couple days to look it over. I'm very reluctant to give it to them again because like I previously said, I've paid them a small fortune. Their computers say the misfires are on cylinders 1 and 5 and they are wanting to do a compression check.

Someone please give me some advice. What could the problem be? There are really no other reputable shops in my area to take it to. :cry

 

[6 Shooter]

That's the way ya got it back from them?

 

[TantricLT4]

I don't think I understand your question..

They've given the car back to me twice - each time they've shown me on their computer that it was not throwing any codes. The next day.. multiple misfires.

I see you're from Lebanon - I'm from Springfield. Do you know of any good shops?

 

[6 Shooter]

These guys should be able to hook ya up . . .

http://www.corvettesunlimited.com/location.htm​

Corvettes Unlimited
1967 West Boat Street
Ozark, MO 65721
Everett Brewer - President
PHONE: (417)581-8786 FAX: (417)581-2726

 

[JEFNLSA]

They've given the car back to me twice - each time they've shown me on their computer that it was not throwing any codes. The next day.. multiple misfires.

I'm guessin' that is because they've cleared the code/s out beforehand but by the next day they re-set themselves.

Is it the PO300 Random Multiple Misfire code?

I had that problem w/ mine but it was due to the Hotcam...had the code eliminated when I had the custom tune done.

If yours is stock, I'd replace the plugs & wires. That may do the trick. Those misfire codes are a PITA! With a new opti on a stock motor you shouldn't be getting misfire codes.

Wish I could offer more...

 

[Vettelt193]

I don't understand the no codes thing... OBDII saves the codes into history. they should be able to see them even if they aren't currently happening.

I would check the plug wires yourself one more time, just to make sure they used dielectric grease in the boots. could be as simple as a bad connection(s)

 

[TantricLT4]

Thanks for the response Jeff..

They do clear the codes.. and yes they are reset the next day..

Im not exactly sure the specific code.. Like i said, they check the plugs and wires (the plugs were changed 6 months ago and the wires are relatively new MSD wires)

The car is essentially stock - forced air intake, larger throttle body, headers, hi-flow cats, true duals -> flowmasters, short throw shifter, MSD 6A (that recently went bad on me, now is bypassed not working) 3.73s, and a nitrous wet kit (I've never ran a bottle through it, the previous owner install the kit) Everything in the computer has been reset to stock, so whatever tune it DID have.. it has no longer...

Anyone else have any ideas what could be wrong?

 

[TantricLT4]

I don't understand the no codes thing... OBDII saves the codes into history. they should be able to see them even if they aren't currently happening.

I would check the plug wires yourself one more time, just to make sure they used dielectric grease in the boots. could be as simple as a bad connection(s)

Yea, I guess I need to get my hands dirty.. It just seems that they should have done that themselves.. (and like I said, they told me they checked the plugs and wires).. its frusterating

 

[Vettelt193]

Yea, I guess I need to get my hands dirty.. It just seems that they should have done that themselves.. (and like I said, they told me they checked the plugs and wires).. its frusterating

I'd pull one wire off a plug, just to see if they did what they were supposed to. 99 cents worth of grease goes a long way, and some of these dealer techs cut corners. heck, some dealers just want more of your money.

 

[TantricLT4]

heck, some dealers just want more of your money.

This is why I'm reluctant to take it back to them. They have a reputation..

Thanks for the idea..

 

[TantricLT4]

No-one else has had this problem?

 

[gmjunkie]

No-one else has had this problem?

Yes!! I have seen problem's Like this!! But I have Yet to Change a Opti-Spark !! If I knew the Code's this may help!! Sometimes it takes Day's to Fig. out!! I have However Changed or had Flashed Lot's of ECM's on theas Car's!! A ECM "WILL LIE TO YOU" not always,but 60-70% of time if it itself is the Problem!! I would need it for some Time!! Ground Problem's on C-4's can couse Weard Thing's to happen!! Let me Know what the code's are!! Auto Zone,Advance,O'Reilly all have a Scanner around here!! junk!!p.s. I was born and raised in Kirksville

 

[redc4corvette]

I think you said 1 and 5 have a miss fire?
I think they cought the wires under the powersteering or alt bracket and they may be cut.
It's a tight fit in their and that would be the ones they would screw up on.
1-3-5-7 if they realy cut them up.

 

[TantricLT4]

Ok thanks.. Im gonna try to get a scanner next week (you say I can use one from O'Reilly's?) I've got a buddy that's gonna help me out..

I never thought about them being cut.. I'll definitely check that too.

Thanks guys!